Communications systems of this type for the direct exchange of information between motor vehicles already form a communication platform for a wide spectrum of information services and transport telematics applications. In particular, diverse proposals are already known from the state of the art for optimising the flow of traffic based on stationary data, but particularly also based on data established by motor vehicles, about the traffic situation.
Road traffic is one of the most important and complex systems of our modern world. The levels of complexity which occur in this context range from individual actions by individual motor vehicle drivers, through local phenomena such as density variations and traffic congestion, the choice of driving route and driving time by the road user, local and temporal traffic patterns and national traffic flows, to long-term traffic development and traffic regulation.
Particular challenges are presented by the complex interaction between the numerous road users. This results in complicated phenomena which are difficult to control and adversely affect the flow of traffic in a very undesirable fashion. An example of this is a traffic jam where, for various reasons, with high densities of motor vehicles, the traffic is reduced to a stop-and-go manner of driving. This entails a reduced flow of traffic, increased journey times, stressful situations for drivers and an increased risk of accidents.
These problems have a particularly serious impact due to the increased energy consumption associated therewith and the environmental pollution resulting therefrom.
Communications systems between a plurality of motor vehicles are devised as an ad-hoc network. Therefore, they do not depend on any pre-installed network infrastructure and allow in particular the exchange of data in the local or regional surroundings of a motor vehicle.
In addition to typical Internet and telematics applications, these radio networks will support traffic-based applications, for example danger warnings and cooperative driver assistance systems. The communication via a plurality of motor vehicles opens up a new dimension for the provision of telematics applications, in that data of systems of vehicles travelling ahead is made available, such as the driving situation, detected by sensors, of the motor vehicle or data from camera or radar systems.
DE 10 2007 053 738 A1 generally discloses a vehicle-to-vehicle communication device for communication between motor vehicles, in which the transmitting vehicle passes on not only its own data, but also information about adjacent vehicles.
Furthermore, US 2005/0225457 A1 discloses a method in which not only the positional information of a vehicle equipped with the communication device is transmitted, but also the positional information of surrounding, correspondingly equipped vehicles which is recorded by a camera or the like.
The information is generally represented by visualisation on a display. For example, pictograms with an information content of, for example “risk of congestion” or “road works” are used for this purpose. DE 102 00 883 B4 discloses a method for representing information on a screen, for example on the screen of a navigation device in a motor vehicle.
In recent years, some approaches have been developed which focus on the individual driver. These include so-called assistance systems which are to ensure enhanced driving comfort and increased safety. Examples are for example tempostats, also called “cruise control”. Recently, advanced approaches have also been developed, known as “adaptive cruise control”, which also consider the driving behaviour, detected by sensors installed in the vehicle, of the vehicle which is immediately in front.
Thus, DE 103 49 434 A1 discloses how such a distance and speed regulation in stop-and-go situations can be brought into a different mode to avoid a constant jerky movement of vehicles stopping and starting. Methods of this type are based on information detected by appropriate sensors of the motor vehicle, and in particular on the speed of said vehicle. An exchange of information between a plurality of motor vehicles is not provided in this case.
According to the teaching of DE 10 2005 050 277 A1, the behaviour of a vehicle driving ahead is also detected by sensors.
DE 10 2007 037 329 A1 describes a method for determining a driving strategy to optimise the operating costs, in particular the fuel consumption. For this purpose, information can be detected by sensors of the vehicle and measures can be indicated to improve the operating state. The method is an optimisation of different parameters which are assumed to be known and which play a part in the choice of route.
DE 101 30 768 C2 discloses a channel access method for ad-hoc radio networks for the exchange of data between vehicles.
Furthermore, DE 197 50 942 A1 discloses a method and a device for determining a driving strategy as information for the driver of a motor vehicle, information of other motor vehicles being recorded by a receiving means and information derived therefrom for the vehicle driver is provided as a signal for reducing the speed.
In addition, DE 100 29 816 A1 relates to a driver-assisting system for an optimum manner of driving. To calculate the driving recommendations, data for detecting the driver's own driving situation and the traffic situation which lies ahead is considered while including GPS data to establish the current vehicle location and including digital road maps to ascertain the local layout of the road and an output of computer-assisted driving recommendations to the system user who is calling up.
Furthermore, technical systems known as traffic-influencing installations are also already frequently used on motorways and dual carriageways which improve the flow of traffic on one or more sections or nodes or in the entire network by a collective influence. The objective of traffic-influencing installations is to increase the traffic safety by reducing the speed variance in the vehicle collective and to optimally distribute the journeys over the available infrastructure, in addition to improving the traffic quality for the user and to prevent unstable traffic situations, such as shock waves and traffic jams. Stationary signals and traffic signs are used to convert the connected strategy into visual symbols for the driver, for example to restrict his speed.
The alternating installations, currently used in practice, to influence the traffic suffer from the disadvantage that they provide relatively unspecific speed restrictions which are therefore often unnecessary and are largely disregarded by road users. In the long run, they no longer fulfill their purpose in a traffic jam because generally the traffic is no longer moving fast anyway; the time and energy-consuming stop-and-go waves in the congestion are not prevented thereby.
It would also be possible to provide, in addition to the information about the risk of congestion, information about the exact extent of and the speed of the vehicles involved in the congestion. This type of information provision overburdens the road user and ultimately does not lead to the correct conclusions. Instead, the road user is also diverted from the traffic situation.
However, in practice, because such information is relatively abstract and is often unverifiable by the road user, he/she will initially briefly note said information and then will often completely ignore it.
A further approach is the so-called electronic drawbar by which motor vehicles are to be forced to form exactly synchronised convoys at a relatively high speed and with a small distance. In this way, fast overtaking maneuvers for cars could achieve a reduction in the fuel consumption and thus in environmental pollution with better utilised roads and due to the lower air resistance of the individual vehicles.
The electronically coupled motor vehicle is oriented by means of a computer-assisted image processing system on the vehicle ahead. A video camera records a specific pattern on the rear end of the front vehicle. From this, the computer calculates direction, distance and relative speed and adapts the following vehicle accurately thereto. Alternatively, infrared light sources can also generate the pattern, which does entail an increase in cost, but also an increase in the evaluation reliability for this measure. In addition to the high demands for technical reliability of such systems, a further disadvantage is the question of liability in the case of fault-induced damage.
In principle, macroscopic approaches are too cumbersome and too slow to promptly influence the traffic dynamics. A traffic jam is only recognised when it has already reached a certain size. Added to this is the imprecision of the traffic detection by the restricted stationary measuring points, which suffer from considerable inaccuracies. Even the emerging replacement of the traffic radio by navigation devices only influences the choice of route, thus particularly a bypassing of the congestion, but not the behaviour of the traffic in the traffic jam itself.